Dynamic high voltage (hv) level shifter with temperature compensation for high-side gate driver

ABSTRACT

Various embodiments of the present application are directed towards a level shifter with temperature compensation. In some embodiments, the level shifter comprises a transistor, a first resistor, and a second resistor. The first resistor is electrically coupled from a first source/drain of the transistor to a supply node, and the second resistor is electrically coupled from a second source/drain of the transistor to a reference node. Further, the first and second resistors have substantially the same temperature coefficients and comprise group III-V semiconductor material. By having both the first and second resistors, the output voltage of the level shifter is defined by the resistance ratio of the resistors. Further, since the first and second resistors have the same temperature coefficients, temperature induced changes in resistance is largely cancelled out in the ratio and the output voltage is less susceptible to temperature induced change than the first and second resistors individually.

REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of U.S. application Ser. No.16/140,982, filed on Sep. 25, 2018, which claims the benefit of U.S.Provisional Application No. 62/624,499, filed on Jan. 31, 2018. Thecontents of the above-referenced Patent Applications are herebyincorporated by reference in their entirety.

BACKGROUND

Ultrahigh voltage semiconductor devices are semiconductor devices thatcan sustain operation at voltages of several hundred volts, such as, forexample, voltages around 600 volts. Among other things, ultrahighvoltage semiconductor devices are used for level shifters. Such a levelshifter translates an input signal at a first voltage domain to anoutput signal at a second voltage domain to resolve incompatibilitybetween devices that respectively operate at the first and secondvoltage domains. Level shifters find application in, among other things,power conversion, radiofrequency (RF) power amplifiers, and RF switches.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a circuit diagram of some embodiments of a levelshifter with temperature compensation.

FIG. 2 illustrates a cross-sectional view of some embodiments of thelevel shifter of FIG. 1.

FIGS. 3A-3F illustrate circuit diagrams of various embodiments of a gatedriver circuit in which the level shifter of FIG. 1 finds application.

FIG. 4 illustrates a layout of some embodiments of the gate drivercircuit of FIG. 3A.

FIGS. 5A and 5B illustrate circuit diagrams of the gate driver circuitof FIG. 3A at various states using non-limiting example voltages.

FIG. 6 illustrates a block diagram of some embodiments of a method ofusing a level shifter with temperature compensation.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

A high-voltage level shifter may comprise a p-typemetal-oxide-semiconductor field-effect transistors (MOSFET) and ann-type MOSFET. The p-type and n-type MOSFETs are gated by an inputsignal in a first voltage domain and drains of the p-type and n-typeMOSFETs are electrically coupled to each other at an output node.Further, a source of the n-type MOSFET is electrically coupled to areference node (e.g., ground), and a source of the p-type MOSFET iselectrically coupled to a power supply of a second voltage domain. Dueto the configuration of the p-type and n-type MOSFETs, the p-type MOSFETis an ON state while the n-type MOSFET is in an OFF state and viceversa. Further, an output signal in the second voltage domain isgenerated at the output node. Depending upon which one of the n-type andp-type MOSFETs is in the ON state, the output signal is pulled down tothe reference node or pulled up to the power supply. Challenges with thehigh-voltage level shifter are its large size and high parasitic gatecapacitance, the latter of which limits performance (e.g., switchingspeed).

High-electron-mobility transistors (HEMTs) have smaller form factors andlower parasitic gate capacitances than the p-type and n-type MOSFETs.Therefore, an approach for overcoming the above challenges may be toreplace the p-type and n-type MOSFETs respectively with p-type andn-type HEMTs. A p-type HEMT is a HEMT selectively conducting along atwo-dimensional hole gas (2DHG), whereas an n-type HEMT is a HEMTselectively conducting along a two-dimensional electron gas (2DEG).However, a p-type HEMT is typically not suitable for use due to, amongother things, low p-type (i.e., hole) mobility and the 2DHG bandstructure. Another approach for overcoming the above challenges may beto replace the p-type and n-type MOSFETs respectively with a resistorand an n-type HEMT. However, processes for forming the n-type HEMT aretypically incompatible with processes for forming polysilicon and metalresistors. As such, the resistor is typically formed as a 2DEG resistor,which has a high temperature coefficient and subjects the output of thehigh-voltage level shifter to high variation. Additionally, while then-type HEMT is in the ON state, there is static current from the powersupply to the reference node, which lowers the power efficiency of thehigh-voltage level shifter. The resistance of the resistor may beincreased to reduce the static current. However, increasing theresistance of the resistor increases the RC time constant at the outputof the high-voltage level shifter and reduces switching speed at theoutput. This negates the benefits associated with the low parasiticcapacitance of the n-type HEMT, compared to the n-type MOSFET, such thatthe high-voltage level shifter with the n-type HEMT may have switchingspeed comparable to that of the high-voltage level shifter with then-type MOSFET.

Various embodiments of the present application are directed towards alevel shifter with temperature compensation. In some embodiments, thelevel shifter comprises a transistor, a first resistor, and a secondresistor. The first resistor is electrically coupled from a firstsource/drain of the transistor to a supply node, and the second resistoris electrically coupled from a second source/drain of the transistor toa reference node. Further, the first and second resistors havesubstantially the same temperature coefficients and comprise group III-Vsemiconductor material, the latter of which may lead to high temperaturecoefficients.

By having both the first and second resistors, the output of the levelshifter is defined by the resistance ratio of the resistors. Further,since the first and second resistors have substantially the sametemperature coefficients, resistances of the first and second resistorschange by about the same percentage with changes in temperature. As aresult, temperature induced changes in resistance are largely cancelledout in the ratio and the output of the level shifter is less susceptibleto temperature induced change than the first and second resistorsindividually. Also, by having both the first and second resistors,static current may be reduced without materially impacting switchingspeed at the output of the level shifter. The second resistor may have alarge resistance to reduce static current. The first resistor may have asmall resistance so the RC time constant at output of the level shifteris small. The small RC time constant, in turn, allows fast switchingspeed.

With reference to FIG. 1, a circuit diagram 100 of some embodiments of alevel shifter 102 with temperature compensation is provided. The levelshifter 102 is configured to translate an input signal 104 at a firstvoltage domain to an output signal 106 at a second voltage domain thatis high compared to the first voltage domain. For example, the firstvoltage domain may be about 6 volts or less, whereas the second voltagedomain may be 100s of volts or more. Other voltages are, however,amenable for the first and second voltage domains. The level shifter 102comprises a pull-up resistor 108, a transistor 110, and a pull-downresistor 112.

The pull-up resistor 108 electrically couples a first source/drain ofthe transistor 110 to a supply terminal 114, and the pull-down resistor112 electrically couples a second source/drain of the transistor 110 toa return terminal 116. The first source/drain and the secondsource/drain may, for example, respectively be a drain and a source orvice versa. A power supply (not shown) of the second voltage domain iselectrically coupled from the supply terminal 114 to the return terminal116. The return terminal 116 serves as a reference for the level shifter102 and, in some embodiments, is electrically coupled to ground. A gateof the transistor 110 is electrically coupled to an input terminal 118,and a body of the transistor 110 is electrically coupled to the returnterminal 116. Further, an output terminal 120 is electrically coupledbetween the transistor 110 and the pull-up resistor 108.

During use of the level shifter, the input signal 104 switches between ahigh state and a low state. The high state may, for example, correspondto a power supply voltage of the first voltage domain, whereas the lowstate may, for example, correspond to zero volts. The switching of theinput signal 104 switches the transistor 110 between an ON state and anOFF state. For example, the transistor 110 may be in an ON state and anOFF state respectively when the input signal 104 is in the high stateand the low state or vice versa.

When the transistor 110 is in the OFF state, the voltage at the outputterminal 120 is pulled up towards the voltage at the supply terminal 114via the pull-up resistor 108. Assuming the output terminal 120 iselectrically coupled to a high impedance input, the voltage at theoutput terminal 120 is equal to or about equal to the voltage at thesupply terminal 114 and static current is negligible if not nonexistent.Note that it is assumed the output terminal 120 is electrically coupledto a high impedance input since the assumption simplifies the discussionand since the assumption will often, but not always, hold true.

When the transistor 110 is in the ON state, the voltage at the outputterminal 120 is pulled down towards the voltage at the return terminal116 via the pull-down resistor 112. Assuming the output terminal 120 iselectrically coupled to a high impedance input, the level shifter 102may be modeled as a voltage divider. The assumption simplifies thediscussion and will often, but not always, hold true. When modeling thelevel shifter 102 as a voltage divider, the voltage at the outputterminal 120 may be equal to or about equal to

${\frac{R_{p\; d} + R_{o\; n}}{R_{p\; d} + R_{o\; n} + R_{p\; u}}V_{ps}},$

where R_(pd) is the resistance of the pull-down resistor 112, R_(on) isthe ON resistance of the transistor 110, R_(pu) is the resistance of thepull-up resistor 108, and V_(ps) is the voltage at the supply terminal114. By adjusting the ratio between the resistances of the pull-up andpull-down resistors 108, 112, the voltage at the output terminal 120 maybe controlled. Further, static current flowing along a conductive path122, from the supply terminal 114 to the return terminal 116, may bereduced without materially reducing the switching speed at the outputterminal 120.

Static current along the conductive path 122, from the supply terminal114 to the return terminal 116, may be reduced by increasing theresistance from of the supply terminal 114 to the return terminal 116.Previous level shifters did not have the pull-down resistor 112 andhence achieved this by increasing the resistance of the pull-up resistor108. However, increasing the resistance of the pull-up resistor 108leads to a large RC time constant at the output terminal 120. Theresistance of the RC time constant includes the resistance of thepull-up resistor 108, and the capacitance of the RC time constantincludes parasitic capacitance of the transistor 110 and other parasiticcapacitance at the output terminal 120. The large RC time constant, inturn, leads to poor switching speed at the output terminal 120, which isexacerbated by large voltage swings at the output terminal 120 when thetransistor 110 switches between ON and OFF states. By including thepull-down resistor 112, the resistance from the supply terminal 114 tothe return terminal 116 can be increased by way of the pull-downresistor 112 without materially increasing the RC time constant at theoutput terminal 120. This, in turn, allows static current to be reducedwhile keeping switching speed high.

In some embodiments, the pull-up and pull-down resistors 108, 112 havehigh temperature coefficients. A resistor with a high temperaturecoefficient may, for example, be a resistor that changes in resistanceby more than 1%, 2%, 5%, or some other suitable percent per degreeCelsius change in temperature. In some embodiment, the pull-up andpull-down resistors 108, 112 have the same or substantially the sametemperature coefficients. The temperature coefficients may, for example,be “substantially” the same if each temperature coefficient is within1%, 2%, 5%, or some other suitable percent of the other temperaturecoefficient. In some embodiments, the pull-up and pull-down resistors108, 112 are formed simultaneously by the same process so as to have thesame or substantially the same temperature coefficients.

Where the pull-up and pull-down resistors 108, 112 have high temperaturecoefficients that are the same or substantially the same, thecombination of the pull-up and pull-down resistors 108, 112 providestemperature compensation. Previous level shifters did not have thepull-down resistor 112, whereby the voltage at the output terminal 120was dominated by the resistance of the pull-up resistor 112 while thetransistor 110 was in the ON state. Hence, the voltage at the outputterminal 120 was subject to large variation as the resistance of thepull-up resistor 108 changed with temperature. By including thepull-down resistor 112, the voltage at the output terminal 120 isdominated by the ratio of the pull-up resistor 108 to the pull-downresistor 112. See the above discussion on modeling the level shifter 102as a voltage divider. Since resistances of the pull-up and pull-downresistors 108, 112 change by the same or substantially the samepercentage with temperature, the ratio between the resistances of thepull-up and pull-down resistors 108, 112 is less susceptible to changein temperature. As a result, the voltage at the output terminal 120 isless susceptible to changes in temperature.

In some embodiments, the pull-up and pull-down resistors 108, 112 havethe same structure, albeit with difference dimensions. In otherembodiments, the pull-up and pull-down resistors 108, 112 have differentstructures. In some embodiments, the pull-up and pull-down resistors108, 112 have the structure of a depletion-mode HEMT without a gateand/or the structure of a depletion-mode metal-insulation-semiconductorfield-effect transistor (MISFET) without a gate. In some embodiments,the pull-up and pull-down resistors 108, 112 comprise individual 2DEGs(not shown) or individual 2DHGs (not shown). In embodiments in which thepull-up and pull-down resistors 108, 112 comprise individualtwo-dimensional carrier gases (i.e., 2DEGs or 2DHGs), the pull-up andpull-down resistors 108, 112 comprise individual heterojunctions alongwhich the two-dimensional carrier gases form. The heterojunctions may,for example, be or comprise gallium nitride (GaN), gallium arsenide,some other suitable group III-V material, or any combination of theforegoing.

In some embodiments, the transistor 110 is a HEMT, a MISFET, or someother suitable transistor. In some embodiments, the transistor 110operates in enhancement mode. In other embodiments, the transistor 110operates in depletion mode. In some embodiments, the transistor 110 hasthe same structure as the pull-up and/or pull-down resistor(s) 108, 112with the addition of a gate structure. In some embodiments, thetransistor 110 comprises and selectively conducts along a 2DEG (notshown), whereby the transistor 110 is n-type. In other embodiments, thetransistor 110 comprises and selectively conducts along a 2DHG (notshown), whereby the transistor 110 is p-type. In embodiments in whichthe transistor 110 comprises a two-dimensional carrier gas (i.e., a 2DEGor a 2DHG), the transistor 110 comprises a heterojunction along whichthe two-dimensional carrier gas forms. The heterojunction may, forexample, be or comprise gallium nitride, aluminum gallium nitride,gallium arsenide, some other suitable group III-V material, or anycombination of the foregoing.

In some embodiments, the pull-up and pull-down resistors 108, 112 are2DEG resistors and the transistor 110 is an n-type HEMT. Further, insome of such embodiments, 2DEGs of the pull-up and pull-down resistors108, 112 and a 2DEG of the n-type HEMT are formed by heterostructurescomprising group III-V materials, such as, for example, GaN or someother suitable material(s). By using group III-V materials for thepull-up and pull-down resistors 108, 112 and the transistor 110, thepull-up and pull-down resistors 108, 112 and the transistor 110 mayoperate at high voltages with small footprints compared to theirsilicon-based counterparts. Further, parasitic capacitance of thetransistor 110 may be lower compared to its silicon-based counterpart,thereby allowing fast switching.

With reference to FIG. 2, a cross-sectional view 200 of some embodimentsof the level shifter circuit 102 of FIG. 1 is provided. The levelshifter circuit 102 is formed on a substrate 202. The substrate 202 may,for example, be or comprise monocrystalline silicon, silicon carbide, orsome other semiconductor material, and/or may, for example, have acrystalline orientation of (111) or some other crystalline orientation.Further, the substrate 202 may, for example, be a bulk semiconductorsubstrate and/or may, for example, be a semiconductor wafer (e.g., a 300or 450 millimeter semiconductor wafer).

A buffer structure 204 overlies the substrate 202, and a heterojunctionstructure 206 overlies the buffer structure 204. The buffer structure204 may, for example, serve to compensate for differences in latticeconstants, crystalline structures, thermal expansion coefficients, orany combination of the foregoing between the substrate 202 and theheterojunction structure 206. The buffer structure 204 may, for example,be or comprise aluminum nitride (AlN), GaN, some other suitable groupIII-V material(s), or any combination of the foregoing. Theheterojunction structure 206 comprises a channel layer 208, and furthercomprises a barrier layer 210 overlying the channel layer 208.

The barrier layer 210 is polarized such that positive charge is shiftedtowards a lower or bottom surface of the barrier layer 210, and negativecharge is shifted towards an upper or top surface of the barrier layer210. The polarization may, for example, result from spontaneouspolarization effects and/or piezoelectric polarization effects. Thebarrier layer 210 may be or comprise, for example, AlN, aluminum galliumnitride (AlGaN), some other group III nitride, some other group III-Vmaterial, or any combination of the foregoing. The channel layer 208directly contacts the barrier layer 210 and is a semiconductor materialwith a band gap unequal to that of the barrier layer 210. Because of theunequal band gaps, the channel layer 208 and the barrier layer 210define a heterojunction 212 at an interface at which the channel layer208 and the barrier layer 210 directly contact. Further, because thebarrier layer 210 is polarized, a 2DEG 214 forms in the channel layer208. The 2DEG 214 extends along the heterojunction 212 and has a highconcentration of mobile electrons, such that the 2DEG 214 is conductive.The channel layer 208 may, for example, be or comprises undoped GaN,some other group III nitride, or some other group III-V material. Insome embodiments, the channel layer 208 is undoped GaN, whereas thebarrier layer 210 is or comprises undoped AlGaN.

The pull-up resistor 108, the transistor 110, and the pull-down resistor112 are on respective portions of the heterojunction structure 206.Electrical isolation between the portions of the heterojunctionstructure 206 may, for example, be achieved by mesa isolation, trenchisolation, or some other suitable isolation. The pull-up resistor 108,the transistor 110, and the pull-down resistor 112 each comprise a pairof electrodes 216, and the transistor 110 further comprises a gatestructure 218. In some embodiments, the electrodes 216 extend throughthe barrier layer 210 to the channel layer 208. In other embodiments,the electrodes 216 overlie the barrier layer 210. The gate structure 218overlies the heterojunction structure 206, laterally spaced from andlaterally between correspond electrodes 216 of the transistor 110. Insome embodiments, the gate structure 218 directly contacts theheterojunction structure 206. In other embodiments, the gate structure218 is separated from the heterojunction structure 206 by a gatedielectric layer (not shown). The electrodes 216 and the gate structure218 are conductive and may be or comprise, for example, aluminum copper,tungsten, copper, some other metal, doped polysilicon, some otherconductive material, or any combination of the foregoing.

While not shown, electrical coupling between the pull-up resistor 108,the transistor 110, and the pull-down resistor 112 may, for example, beachieved by a back-end-of-line (BEOL) interconnect structure overlyingthe electrodes 216 and the gate structure 218. The BEOL interconnectstructure may, for example, comprise a plurality of wires and aplurality of vias alternatingly stacked to define conductive pathsinterconnecting the pull-up resistor 108, the transistor 110, and thepull-down resistor 112 as shown in FIG. 1.

With reference to FIG. 3A, a circuit diagram 300A of some embodiments ofa gate driver circuit in which the level shifter 102 of FIG. 1 findsapplication is provided. The gate driver circuit comprises a high-sidegate driver 302 and a low-side gate driver 304. The high-side gatedriver 302 operates at a high-side voltage domain and is powered by adynamic power supply via a high-side supply node 306 and a high-sidereturn node 308. As discussed hereafter, the dynamic power supply isdefined at least partially by a bootstrap circuit 310 and a high-voltagepower supply (not shown). The low-side gate driver 304 operates at alow-side voltage domain and is powered by a low voltage power supply(not shown) via a low-side supply terminal 312 and a low-side returnterminal 314. The low-side return terminal 314 serves as a reference forthe gate driver circuit and may, for example, be grounded. For ease ofillustration, the low-side supply terminal 312 and the low-side returnterminal 314 each appear multiple times. However, the multiple instancesof the low-side supply terminal 312 are the same terminal, and themultiple instances of the low-side return terminal 314 are the sameterminal.

The high-voltage power supply supplies a high voltage relative to lowvoltage power supply. For example, the high-voltage power supply maysupply 650 volts or more, whereas the low voltage power supply maysupply 6 volts or less. Other voltages are, however, amenable. Further,the high-voltage power supply and the low voltage power supply may, forexample, be DC power supplies or some other suitable power supplies.

The high-side gate driver 302 gates a high-side power transistor 316,and the low-side gate driver 304 gates a low-side power transistor 318.A first source/drain of the high-side power transistor 316 iselectrically coupled to a high-voltage supply terminal 320, whereas asecond source/drain of the high-side power transistor 316 iselectrically coupled to the high-side return node 308. The high-voltagepower supply is electrically coupled from the high-voltage supplyterminal 320 to the low-side return terminal 314 to bias thehigh-voltage supply terminal 320 with a high voltage. A firstsource/drain of the low-side power transistor 318 is electricallycoupled to the high-side return node 308, and a second terminal of thelow-side power transistor 318 is electrically coupled to the low-sidereturn terminal 314. The high-side and low-side power transistors 316,318 may, for example, be power MOSFETs, insulated-gate bipolartransistors (IGBTs), or some other suitable power transistors capable ofsustained operation at the high voltages of the high-voltage powersupply.

Additionally, the high-side gate driver 302 is controlled by a high-sideinput signal at a high-side input terminal 322, and the low-side gatedriver 304 is controlled by a low-side input signal at a low-side inputterminal 324. The high-side and low-side input signals are both at thelow-side voltage domain and switch between a low state and a high state.The low state may, for example, correspond to the voltage at thelow-side return terminal 314, and the high state may, for example,correspond to the voltage at the low-side supply terminal 312. Dependingupon whether the high-side input signal is in the high state or lowstate, the high-side gate driver 302 enables or disables the high-sidepower transistor 316. Similarly, depending upon whether the low-sideinput signal is in the high state or low state, the low-side gate driver304 enables or disables the low-side power transistor 318. Further, thehigh-side and low-side input signals are generated so the high-sidepower transistor 316 is only in the ON state while the low-side powertransistor 318 is in the OFF state and vice versa

Since the high-side input signal is at the low-side voltage domain andthe high-side gate driver 302 operates at the high-side voltage domain,the high-side input signal is incompatible with the high-side gatedriver 302. Therefore, the level shifter 102 is used to translate theinput signal from the low-side voltage domain to the high-side voltagedomain. Operation of the level shifter 102 is as described in FIG. 1,but the high-side input terminal 322 corresponds to the input terminal118 of FIG. 1, the low-side return terminal 314 corresponds to thereturn terminal 116 of FIG. 1, and the high-side supply node 306corresponds to the supply terminal 114 of FIG. 1. Further, in someembodiments, a resistance ratio between the pull-up resistor 108 and thepull-down resistor 112 is selected so a voltage across the pull-upresistor 108 is about equal to the voltage at the low-side supplyterminal 312 when the high-side is in the ON state.

A shaper 326 reshapes an output signal of the level shifter 102 toimprove the slew rate of the output signal. By improving the slew rate,the shaper 326 allows faster switching of the high side between the ONstate and the OFF state. The shaper 326 is powered by the dynamic powersupply and comprises a shaper transistor 328 and a shaper resistor 330.A first source/drain of the shaper transistor 328 is electricallycoupled to the high-side supply node 306 via the shaper resistor 330,and a second source/drain of the shaper transistor 328 is electricallycoupled to the high-side return node 308. Further, a gate of the shaper326 is electrically coupled to an output 332 of the level shifter 102,such that it should be appreciated that output 332 is electricallycoupled to a high impedance input. The output 332 of the level shifter102 may, for example, correspond to the output terminal 120 of FIG. 1.In some embodiments, the shaper resistor 330 is as the pull-up andpull-down resistors 108, 112 of the level shifter 102 are described withregard to FIG. 1 and/or is a group III-V 2DEG resistor. In someembodiments, the shaper transistor 328 is as the transistor 110 of thelevel shifter 102 is described with regard to FIG. 1 and/or is a groupIII-V 2DEG transistor.

The shaper 326 operates similar to the level shifter 102 in that itselectively pulls the voltage at a shaper output 334 up or downdepending upon whether the shaper transistor 328 is in an ON state or anOFF state. For example, the voltage at the shaper output 334 is pulledup towards the voltage of the high-side supply node 306 when the shapertransistor 328 is in the OFF state, and the voltage at the shaper output334 is pulled down towards the voltage at the high-side return node 308when the shaper transistor 328 is in the ON state. Further, the shapertransistor 328 is in the ON state or the OFF state depending on whetherthe output 332 of the level shifter 102 is in the high state or the lowstate. Therefore, the shaper output 334 recreates the output 332 of thelevel shifter 102. In some embodiments, the shaper output 334 isinverted relative to the output 332 of the level shifter 102.

A latch 336 latches the shaper output 334 to filter noise at the shaperoutput 334. By filtering noise, the latch 336 allows faster switching ofthe high side between ON and OFF states. The latch 336 is powered by thedynamic power supply and comprises a pair of latch transistors 338 and apair of latch resistors 340. Each of the latch transistors 338 has afirst source/drain electrically coupled to the high-side supply node 306by a respective one of the latch resistors 340, and further has a secondsource/drain electrically coupled to the high-side return node 308.Further, a gate of a first one of the latch transistors 338 iselectrically coupled to the shaper output 334 and the first source/drainof a second one of the latch transistors 338, while a gate of the secondone of the latch transistors 338 is electrically coupled to the firstsource/drain of the first one of the latch transistors 338 and a latchoutput 342. In some embodiments, the latch resistors 340 are as thepull-up and pull-down resistors 108, 112 of the level shifter 102 aredescribed with regard to FIG. 1 and/or are group III-V 2DEG resistors.In some embodiments, the latch transistors 338 are as the transistor 110of the level shifter 102 is described with regard to FIG. 1 and/or aregroup III-V 2DEG transistors.

The latch transistors 338 are connected so as to create a feedback loop.For example, an output of the first one of the latch transistors 338feeds back to gate of the second one of the latch transistors 338 andvice versa. When the shaper output 334 is in a first state (e.g., a highstate), the feedback loop moves the latch output 342 towards a firststeady state. Similarly, when the shaper output 334 is in a secondstate, the feedback loop moves the latch output 342 towards a secondsteady state. Assuming the shaper output 334 persists in a state for aminimum amount of time, the feedback loop reaches the first or secondsteady state. At steady state, the latch 336 resists change and persistsat steady state until the shaper output 334 changes for the minimumamount of time. The resistance to change allows the latch 336 to filternoise.

As noted above, the dynamic power supply powering the shaper 326, thelatch 336, and the high-side gate driver 302 is partially defined by thebootstrap circuit 310 and the high-voltage power supply (not shown). Thebootstrap circuit 310 comprises a bootstrap capacitor 344 and abootstrap diode 346. A first terminal of the bootstrap capacitor 344 iselectrically coupled to the high-side supply node 306, and a secondterminal of the bootstrap capacitor 344 is electrically coupled to thehigh-side return node 308. An anode of the bootstrap diode 346 iselectrically coupled to the low-side supply terminal 312, and a cathodeof the bootstrap diode 346 is electrically coupled to the high-sidesupply node 306.

During use of the gate driver circuit, a load (not shown) iselectrically coupled from the high-side return node 308, via a loadterminal 348, to the low-side return terminal 314. In some, but not all,embodiments, the load is an inductive load and/or an electric motor.Further, the high-side input signal at the high-side input terminal 322and the low-side input signal at the low-side input terminal 324 aregenerated so the high-side power transistor 316 is only in the ON statewhile the low-side power transistor 318 is in the OFF state and viceversa.

When the low-side power transistor 318 is in the ON state and thehigh-side power transistor 316 is in the OFF state, the high-side returnnode 308 is electrically coupled to the low-side return terminal 314 viathe low-side power transistor 318. Therefore, the low-side returnterminal 314 and the high-side return node 308 are at about the samevoltage. Since the low-side return terminal 314 is the reference for thegate driver circuit, the low-side return terminal 314 and the high-sidereturn node 308 are at about zero volts. Further, since the load (notshown) is electrically coupled from the high-side return node 308 to thelow-side return terminal 314, the voltage across the load is about zeroand the load is disabled.

Also, when the low-side power transistor 318 is in the ON state and thehigh-side power transistor 316 is in the OFF state, the bootstrapcapacitor 344 is charged and the voltage at the low-side supply terminal312 is higher than the voltage at the high-side supply node 306. Assuch, the bootstrap diode 346 is in a non-blocking state. Further, anelectrical path extends from the low-side supply terminal 312, throughthe bootstrap capacitor 344, to the high-side return node 308 (orequivalent to the low-side return terminal 314 at the instant state),such that the bootstrap capacitor 344 is charged to about the voltage atthe low-side supply terminal 312. For example, the bootstrap capacitor344 may be charged to about 6 volts or some other suitable voltage. Asthe bootstrap capacitor 344 is charged, the voltage at the high-sidesupply node 306 increases to about the voltage at the low-side supplyterminal 312.

When the low-side power transistor 318 is in the OFF state and thehigh-side power transistor 316 is in the ON state, the high-voltagesupply terminal 320 is electrically coupled to the high-side return node308 via the high-side power transistor 316. Therefore, the high-voltagesupply terminal 320 and the high-side return node 308 are at about thesame voltage. Further, the voltage at the high-side supply node 306 isequal to or about equal to the voltage at the high-side return node 308plus the voltage across the bootstrap capacitor 344. For example, thevoltage at the high-side return node 308 may, for example, be about 650volts, and the voltage at the high-side supply node 306 may, forexample, be about 656 volts. Other voltages are, however, amenable.Since the load (not shown) is electrically coupled from the high-sidereturn node 308 to the low-side return terminal 314, the voltage acrossthe load is about that of the high-voltage supply terminal 320 and theload is enabled.

Also, when the low-side power transistor 318 is in the OFF state and thehigh-side power transistor 316 is in the ON state, the voltage at thelow-side supply terminal 312 is lower than that at the high-side supplynode 306. As such, the bootstrap diode 346 is in a blocking state thatelectrically isolates the low-side supply terminal 312 and thehigh-voltage supply terminal 320. Absent this isolation, damage mayoccur to power supplies electrically coupled respectively to thelow-side supply terminal 312 and the high-voltage supply terminal 320.

As seen above, the voltages at the high-side supply node 306 and thehigh-side return node 308 vary in accordance with a dynamic powersupply. By using the dynamic power supply, and/or by adjusting theresistance ratio between the pull-up and pull-down resistors 108, 112,the voltage across the pull-up resistor 108 may be reduced. This may,for example, enhance switching speed at the output 332 of the levelshifter 102. Further, by using the dynamic power supply, the voltagedifference between the high-side supply node 306 and the high-sidereturn node 308 is small even when the high-side supply node 306 and thehigh-side return node 308 are at high voltages. For example, thevoltages at the high-side supply node 306 and the high-side return node308 may respectively be about 656 volts and 650 volts, such that thevoltage difference is about 6 volts. Other voltages are, however,amenable. Due to the small voltage difference, components at the highside may be designed for operation at low voltages. Such componentsinclude, for example, the shaper 326, the latch 336, and the high-sidegate driver 302. Since the components at the high side may be designedfor operation at low voltages, design constraints may be relaxed.Further, the size of the components may be reduced.

With reference to FIG. 3B, a cross-sectional view 300B of somealternative embodiments of the gate driver circuit of FIG. 3A isprovided in which a bootstrap transistor 350 is used in place of thebootstrap diode 346 of FIG. 3A. In such embodiments, a controller (notshown) is electrically coupled to a gate of the bootstrap transistor 350via a bootstrap terminal 352. The controller enables the bootstraptransistor 350 while the low-side power transistor 318 is in the ONstate and the high-side power transistor 316 is in the OFF state tocharge the bootstrap capacitor 344. Further, the controller disables thebootstrap transistor 350 while the low-side power transistor 318 is inthe OFF state and the high-side power transistor 316 is in the ON stateto electrically separate the low-side supply terminal 312 from thehigh-side supply node 306. Using the controller and the bootstraptransistor 350 in place of the bootstrap diode 346 allows the low-sidesupply terminal 312 to be electrically coupled to and electricallyseparated from the high-side supply node 306 faster than would bepossible with the bootstrap diode 346. This, in turn, allows fasterswitching of the high-side and low-side power transistors 316, 318between high and low states. In some embodiments, the bootstraptransistor 350 is as the transistor 110 is described with regard toFIG. 1. Further, in some embodiments, the bootstrap transistor 350 is agroup III-V 2DEG transistor.

With reference to FIG. 3C, a cross-sectional view 300C of somealternative embodiments of the gate driver circuit of FIG. 3B isprovided in which the bootstrap transistor 350 is diode connected. Inthe diode connected configuration, a gate of the bootstrap transistor350 is electrically coupled to a drain of the bootstrap transistor 350,which is electrically coupled to the low-side supply terminal 312.Further, in the diode connected configuration, the bootstrap transistor350 acts as the bootstrap diode 346 is described with regard to FIG. 3A.

With reference to FIG. 3D, a cross-sectional view 300D of somealternative embodiments of the gate driver circuit of FIG. 3A isprovided in which the latch 336 of FIG. 3A is omitted. As such, theshaper output 334 of the shaper 326 feeds into the high-side gate driver302 to control the high-side gate driver 302.

With reference to FIG. 3E, a cross-sectional view 300E of somealternative embodiments of the gate driver circuit of FIG. 3A isprovided in which the shaper 326 of FIG. 3A and the latch 336 of FIG. 3Aare omitted. As such, the output 332 of the level shifter 102 feeds intothe high-side gate driver 302 to control the high-side gate driver 302.

With reference to FIG. 3F, a cross-sectional view 300F of somealternative embodiments of the gate driver circuit of FIG. 3A isprovided in which a flip flop 354 is used in place of the latch 336 ofFIG. 3A. The flip flop 354 allows a high-side input signal 356 at thehigh-side input terminal 322 to be pulsed or alternating coupled (AC)coupled, which aids in eliminating static current at level shifters 102of the gate driver circuit. To accommodate the flip flop 354, thehigh-side input terminal 322 is electrically coupled to an edge pulsegenerator 358. The edge pulse generator 358 generates a rising-edgesignal 360 and a falling-edge signal 362 from the high-side input signal356. The rising-edge signal 360 comprises a pulse at each rising edge ofthe high-side input signal 356, and the falling-edge signal 362comprises a pulse at each falling edge of the high-side input signal356.

Two level shifters 102 respectively receive the rising-edge signal 360and the falling-edge signal 362 as inputs. The level shifters 102 areeach as described with regard to FIG. 1, such that each of the levelshifters 102 comprises a pull-up resistor 108, a transistor 110, and apull-down resistor 112. For ease of illustration, the pull-up resistor108 is only labeled for one of the level shifters 102, the transistor110 is only labeled for one of the level shifters 102, and the pull-downresistor 112 is only labeled for one of the level shifters 102. Theoutputs 332 of the level shifters 102 respectively control shapers 326.For ease of illustration, only one of the outputs 332 of the levelshifters 102 is labeled 332.

The shapers 326 are grouped into a first shaper stage 364 and a secondshaper stage 366, each comprising two of the shapers 326. The shapers326 are each as described with regard to FIG. 3A, such that each of theshapers 326 comprises a shaper resistor 330 and a shaper transistor 328.For ease of illustration, the shaper resistor 330 is only labeled forsome of the shapers 326 and the shaper transistor 328 is only labeledfor some of the shapers 326. The two shapers 326 of the first shaperstage 364 respectively receive the outputs 332 of the level shifters102, and the shapers 326 of the second shaper stage 366 respectivelyreceive the shaper outputs 334 of the first shaper stage 364. The shaperoutputs 334 of the second shaper stage 366 control the flip flop 354.For ease of illustration, only some of the shaper outputs 334 arelabeled 334.

The flip flop 354 is powered by the dynamic power supply and comprises apair of storage transistors 368, a pair of flip flop resistors 370, aset transistor 372, and a reset transistor 374. For ease ofillustration, only one of the storage transistors 368 is labeled 368 andonly one of the flip flop resistors 370 is labeled 370. Each of thestorage transistors 368 has a first source/drain electrically coupled tothe high-side supply node 306 by a respective one of the flip flopresistors 370, and further has a second source/drain electricallycoupled selectively to the high-side return node 308 by a respective oneof the set and reset transistors 372, 374. A gate of a first one of thestorage transistors 368 is electrically coupled to the firstsource/drain of a second one of the storage transistors 368, while agate of the second one of the storage transistors 368 is electricallycoupled to the first source/drain of the first one of the storagetransistors 368 and a flip flop output 376. The gates of the set andreset transistors 372, 374 are electrically coupled respectively to theshaper outputs 334 of the second shaper stage 366. In some embodiments,the flip flop resistors 370 are as the pull-up and pull-down resistors108, 112 of the level shifter 102 are described with regard to FIG. 1and/or are group III-V 2DEG resistors. In some embodiments, the storagetransistors 368, the set transistor 372, the reset transistor 374, orany combination of the foregoing is/are as the transistor 110 of thelevel shifter 102 is described with regard to FIG. 1 and/or is/are groupIII-V 2DEG transistors.

The storage transistors 368 are connected so as to create a feedbackloop. For example, an output of the first one of the storage transistors368 feeds back to gate of the second one of the storage transistors 368and vice versa. Based on stimuli from the set and reset transistors 372,374, the feedback loop switches between steady states at the flip flopoutput 376. When the set transistor 372 is activated, the feedback loopmoves the flip flop output 376 to a first steady state. When the resettransistor 374 is activated, the feedback loop moves the flip flopoutput 376 towards a second steady state.

While FIGS. 3D-3F are illustrated using the bootstrap diode 346, thebootstrap diode 346 in any one of FIGS. 3D-3F may be replaced by thebootstrap transistor 350 in FIG. 3B. while FIGS. 3D-3F are illustratedusing the bootstrap diode 346, the bootstrap diode 346 in any one ofFIGS. 3D-3F may be replaced by the bootstrap transistor 350 in FIG. 3C.While FIG. 3F is illustrated with two shaper stages 364, 366, more orless shaper stages are amenable. While FIGS. 3A-3D are illustrated withone shaper stage, more shaper stages are amenable.

With reference to FIG. 4, a layout 400 of some embodiments of the gatedriver circuit of FIG. 3A is provided. The level shifter 102, thelow-side gate driver 304, the shaper 326, the latch 336, and thehigh-side gate driver 302 are integrated together into a commonintegrated circuit (IC) chip 402. Because the shaper 326, the latch 336,and the high-side gate driver 302 are powered by a dynamic power supplyoperating at a different voltage domain than the level shifter 102 andthe low-side gate driver 304, an isolation region 404 may, for example,be employed. The isolation region 404 demarcates a high-side area 406 ofthe IC chip 402 within which the shaper 326, the latch 336, and thehigh-side gate driver 302 are located, and further demarcates a low-sidearea 408 of the IC chip 402 within which the level shifter 102 and thelow-side gate driver 304 are located. The isolation region 404 may, forexample, be or comprise a trench isolation region, a mesa isolationregion, or some other suitable isolation region.

A controller 410 is external to the IC chip 402 and generates ahigh-side input signal 412 and a low-side input signal 414. Thehigh-side input signal 412 indirectly controls the high-side powertransistor 316 through the level shifter 102, the shaper 326, the latch336, and the high-side gate driver 302, whereas the low-side inputsignal 414 indirectly controls the low-side power transistor 318 throughthe low-side gate driver 304. Similar to the controller 410, thehigh-side and low-side power transistors 316, 318 may, for example, beexternal to the IC chip 402. The high-side and low-side powertransistors 316, 318 are employed to selectively enable a load 416.

While FIG. 4 is illustrated using embodiments of the gate driver circuitin FIG. 3A, it is to be understood that embodiments of the gate drivercircuit in any one of FIGS. 3B-3F may also be used. For example, whereembodiments of the gate driver circuit in FIG. 3D are used, the latch336 is omitted from the high-side area 406. As another example, whereembodiments of the gate driver circuit in FIG. 3F are used, the latch336 is replaced with a flip flop and additional shapers. As yet anotherexample, where embodiments of the gate driver circuit in FIG. 3E areused, the latch 336 and the shaper 326 are omitted from the high-sidearea 406.

With reference to FIGS. 5A and 5B, circuit diagrams 500A, 500B of someembodiments of the gate driver circuit of FIG. 3A at various states areprovided using non-limiting example voltages. FIG. 5A illustrate thegate driver circuit in an OFF state, whereas FIG. 5B illustrates thegate driver circuit in an ON state. By the OFF state of the gate drivercircuit, it is meant that the load (not shown) driven by the gate drivercircuit is in the OFF state. Similarly, by the ON state of the gatedriver circuit, it is meant that the load driven by the gate drivercircuit is in the ON state. As discussed above, the load is electricallycoupled from the load terminal 348 to the low-side return terminal 314.

With specific reference to the circuit diagram 500A of FIG. 5A, thehigh-voltage supply terminal 320 is biased at about 650 volts by ahigh-voltage power supply (not shown), and the low-side supply terminal312 is biased at about 6 volts by a low voltage power supply (notshown). Further, a high-side input signal at the high-side inputterminal 322 and a low-side input signal at the low-side input terminal324 are at about 0 volts.

The high-side and low-side input signals respectively control thehigh-side power transistor 316 and the low-side power transistor 318 toenable or disable the load (not shown). The high-side and low-side inputsignals are generated at a low-side voltage domain defined by the lowvoltage power supply (not shown), such that the high-side and low-sideinput signals vary between about 0 volts and about 6 volts dependingupon a state of the gate driver circuit. Further, the high-side andlow-side input signals are generated so the high-side power transistor316 is in the OFF state, while the low-side power transistor 318 is inthe ON state, and vice versa. To have the high-side and low-side powertransistors 316, 318 simultaneously in the ON states leads to a lowimpedance path from the high-voltage supply terminal 320 to the low-sidereturn terminal 314 that may damage the high-voltage power supply (notshown).

The about 0 volts at the low-side input terminal 324 triggers thelow-side gate driver 304 to output about 6 volts to a gate of thelow-side power transistor, assuming the low-side gate driver 304 isinverting. In other embodiments, the low-side gate driver 304 isnon-inverting. The about 6 volts at the output of the low-side gatedriver 304, in turn, enables the low-side power transistor 318. As aresult, the voltages respectively at the high-side return node 308 andthe low-side return terminal 314 are about the same. This, in turn,disables the load (not shown) since the voltage across the load is about0 volts. Further, since the low-side return terminal 314 is thereference for the gate driver circuit, the voltages respectively at thehigh-side return node 308 and the low-side return terminal 314 are about0 volts.

The about 0 volts at the high-side input terminal 322 disables thetransistor 110 of the level shifter 102. As a result, the pull-downresistor 112 is electrically isolated from the output 332 of the levelshifter 102 by the transistor 110 of the level shifter 102. Further, thevoltage at the output 332 of the level shifter 102 is pulled up by thepull-up resistor 108 towards the voltage at the high-side supply node306. Since the output 332 of the level shifter 102 is electricallycoupled to a gate of the shaper 326, which is a high impedance input,the voltage at the output 332 of the level shifter 102 is about the sameas the voltage at the high-side supply node 306. As illustrated, thevoltages respectively at the high-side supply node 306 and the output332 of the level shifter 102 are about 6 volts. However, when firsttransitioning to about 0 volts at high-side input terminal 322, thevoltages respectively at the high-side supply node 306 and the output332 of the level shifter 102 are less than about 6 volts.

The voltages respectively at the high-side supply node 306 and theoutput 332 of the level shifter 102 are defined by the voltage acrossthe bootstrap capacitor 344 since the high-side return node 308 is atabout 0 volts. Further, the bootstrap capacitor 344 is previouslydischarged when first transitioning to about 0 volts at high-side inputterminal 322. Therefore, voltage at the high-side supply node 306 isless than about 6 volts when first transitioning to 0 volts at high-sideinput terminal 322. The voltages respectively at the high-side supplynode 306 and the output 332 of the level shifter 102 reach about 6 voltsafter the bootstrap capacitor 344 is completely charged. The bootstrapcapacitor 344 is charged along a conductive path 502 that extends fromthe low-side supply terminal 312, through the bootstrap diode 346, thebootstrap capacitor 344, and the low-side power transistor 318, to thelow-side return terminal 314. Because the voltage at the high-sidesupply node 306 is less than the voltage at the low-side supply terminal312 (e.g., 3 volts vs. 6 volts) when first transitioning to 0 volts athigh-side input terminal 322, the bootstrap diode 346 is in a non-blockstate that allows the charging of the bootstrap capacitor 344.

The about 6 volts at the output 332 of the level shifter 102 gates theshaper transistor 328 of the shaper 326. This enables the shapertransistor 328, which pulls down the voltage at the shaper output 334 ofthe shaper 326 to the about 0 volts at the high-side return node 308.The about 0 volts at the shaper output 334 gates a first one of thelatch transistors 338, thereby setting the first one of the latchtransistors 338 to the OFF state. Since the first one of the latchtransistors 338 is in the OFF state, the corresponding one of the latchresistors 340 pulls the latch output 342 towards the voltage at thehigh-side supply node 306. Further, since the latch output 342 iselectrically coupled to high impedance inputs, the voltage at the latchoutput 342 is at the about 6 volts at the high-side supply node 306.These high impedance inputs include the input of the high-side gatedriver 302 and the gate of a second one of the latch transistors 338.

The about 6 volts at the gate of the second one of the latch transistors338 enables the second one of the latch transistors 338, whichelectrically couples the shaper output 334 to the low-side return node308. Additionally, the about 6 volts at the input of the high-side gatedriver 302 triggers the high-side gate driver 302 to output about 0volts to a gate of the high-side power transistor 316, assuming thehigh-side gate driver 302 is inverting. In other embodiments, thehigh-side gate driver 302 is non-inverting. The about 0 volts at theoutput of the high-side gate driver 302, in turn, disables the high-sidepower transistor 316. Further, since the high-side power transistor 316is disabled, the high-side power transistor 316 electrically separatesthe high-voltage supply terminal 320 from the high-side return node 308.

With specific reference to the circuit diagram 500B of FIG. 5B, thehigh-voltage supply terminal 320 is still biased at about 650 volts by ahigh-voltage power supply (not shown), and the low-side supply terminal312 is still biased at about 6 volts by a low voltage power supply (notshown). However, in contrast with the circuit diagram 500B of FIG. 5B,the high-side input signal at the high-side input terminal 322 and thelow-side input signal at the low-side input terminal 324 are at about 6volts.

The about 6 volts at the low-side input terminal 324 triggers thelow-side gate driver 304 to output about 0 volts to a gate of thelow-side power transistor 318, assuming the low-side gate driver 304 isinverting. In other embodiments, the low-side gate driver 304 isnon-inverting. The about 0 volts at the output of the low-side gatedriver 304, in turn, disables the low-side power transistor 318. As aresult, the high-side return node 308 and the low-side return terminal314 are electrically separated by the low-side power transistor 318.

When first transitioning to about 6 volts at the high-side inputterminal 322, the high-side power transistor 316 and the low-side powertransistor 318 are in OFF states. As such, the high-side return node 308is essentially floating, assuming the load (not shown) at the loadterminal 348 has a high input impedance. Further, the voltage at thehigh-side supply node 306 is the about 6 volts across the bootstrapcapacitor 344 plus the voltage at the high-side return node 308.Therefore, the voltage at the high-side supply node 306 is at leastabout 6 volts. Over time, the voltage at the high-side return node 308tends to float upward, whereby the voltage at the high-side supply node306 tends to float upward. Therefore, the voltage at the high-sidesupply node 306 tends to exceed the voltage at the low-side supplyterminal 312. Further, the bootstrap diode 346 enters a blocking statethat electrically separates the low-side supply terminal 312 from thehigh-side supply node 306.

The about 6 volts at the high-side input terminal 322 causes a cascadeeffect through the level shifter 102, the shaper 326, the latch 336, andthe high-side gate driver 302 that eventually turns the high-side powertransistor 316 to the ON state using the bootstrap capacitor 344 as apower supply. When the high-side power transistor 316 is turned to theON state, the voltage at the high-side return node 308 is no longerfloating and becomes about the same as the about 650 voltage at thehigh-voltage supply terminal 320. This, in turn, enables the load (notshown) electrically coupled form the load terminal 348 to the low-sidereturn terminal 314. Additionally, when the high-side power transistor316 is turned to the ON state, the voltage at the high-side supply node306 becomes the voltage at the high-side return node 308 plus thevoltage across the bootstrap capacitor 344. For example, the high-sidesupply node 306 becomes about 656 volts when the voltage at thehigh-side return node 308 is about 650 volts.

The cascade effect triggered by the about 6 volts at the high-side inputterminal 322 begins by enabling the transistor 110 of the level shifter102. As a result, static current may flow along a conductive path 504extending from the high-side supply node 306 to the low-side returnterminal 314. Further, the voltage at the output 332 of the levelshifter 102 is pulled down by the pull-down resistor 112 towards thevoltage at the low-side return terminal 314.

Since the output 332 of the level shifter 102 is electrically coupled toa gate of the shaper 326, which is a high impedance input, the levelshifter 102 may be modeled as a voltage divider. Therefore, the voltageat the output 332 of the level shifter 102 may be equal to or aboutequal to

${\frac{R_{p\; d} + R_{o\; n}}{R_{p\; d} + R_{o\; n} + R_{p\; u}}V_{ps}},$

where R_(pd) is the resistance of the pull-down resistor 112, R_(on) isthe ON resistance of the transistor 110, R_(pu) is the resistance of thepull-up resistor 108, and V_(ps) is the at least 6 volts at thehigh-side supply node 306. The ratio of the pull-up and pull-downresistors 108, 112 are selected so the voltage at the output 332 of thelevel shifter 102, relative to the high-side return node 308, is lessthan the threshold voltage of the shaper transistor 328. For example,where the voltage at the high-side supply node 306 and the high-sidereturn node 308 are respectively 656 volts and 650 volts, the resistanceratio of the pull-up and pull-down resistors 108, 112 may be such thatthe voltage across the pull-up resistor 108 is about 6 volts and thevoltage at the output 332 of the level shifter is about 650 volts.

Since the output 332 of the level shifter 102 is at a lesser voltagethan the threshold voltage of the shaper transistor 328, the shapertransistor 328 is in the OFF state and the shaper output 334 of theshaper transistor 328 is pulled up towards the voltage at the high-sidesupply node 306. By pulling up the shaper output 334, the voltage at theshaper output 334 may, for example, be about 656 volts. The latch 336latches the shaper output 334, and the latch output 342 controls thehigh-side gate driver 302. Further, the output of the high-side gatedriver 302 controls the high-side power transistor 316. As in FIG. 5A,the latch 336 and the high-side gate driver 302 are assumed to beinverting, whereby the latch output 342 may, for example, be about 650volts when the shaper output 334 is about 656 volts, and the output ofthe high-side gate driver 302 may be about 656 volts when the latchoutput 342 is about 650 volts.

While FIGS. 5A and 5B are used to describe operation of a gate drivercircuit using embodiments of the gate driver circuit in FIG. 3A, it isto be understood that the description is generally applicable toembodiments of the gate driver circuit in any one of the FIGS. 3B-3F.Differences in the operation of the various embodiments of the gatedriver circuit in FIGS. 3B-3F were emphasized while discussing theindividual embodiments.

With reference to FIG. 6, a block diagram 600 of some embodiments of amethod of using the level shifter and the gate driver circuit of FIG. 3Ais provided.

At 602, a level shifter comprising a pull-up resistor, a pull-downresistor, and a transistor is provided, where the pull-up and pull-downresistors are respectively at source/drain terminals of the transistorand have high temperature coefficients that are approximately the same.The level shifter may typically be modeled as a voltage divider in whichthe output voltage is controlled by the resistance ratio of the pull-upand pull-down resistors. Since the pull-up and pull-down resistors havehigh temperature coefficients that are approximately the same,temperature-induced resistance variations in the ratio largely cancelout and the ratio is minimally affected by temperature variations. As aresult, the voltage output of the level shifter is not prone to largetemperature-induced voltage swings.

At 604, the providing of the level shifter comprises selecting aresistance ratio for the pull-up and pull-down resistors, such that avoltage drop across the pull-up resistor is small compared to a voltagedrop across the pull-down resistor while the transistor is in the ONstate. As such, the resistance of the pull-down resistor is largecompared to the resistance of the pull-up resistor. Resistance of thepull-down resistor may be large to reduce static current while thetransistor is in the ON state. Resistance of the pull-up resistor may besmall to reduce the RC time constant at the output of the level shifter,thereby allowing fast switching speeds at the output of the levelshifter. Therefore, the combination of the pull-up and pull-downresistors allows fast switching at the output of the level shifter whilealso reducing static current.

At 606, a dynamic supply voltage is applied across the level shifter,where the dynamic supply voltage is generated using a bootstrap circuitand is in a dynamic voltage domain alternating between a low voltagedomain and a high voltage domain. The low voltage domain may, forexample, be about 0 volts to about 6 volts, whereas the high voltagedomain may, for example, be about 650 volts to about 656 volts. Othervoltages are, however, amenable. The bootstrap circuit may, for example,be used in conjunction with a high-side gate driver and a low-side gatedriver as illustrated and described with regard to FIGS. 5A and 5B.

At 608, an input signal is applied to the level shifter to generate anoutput signal in the dynamic voltage domain, where the input signal isin the low voltage domain.

At 610, the output signal is shaped to generate a shaped output signalwith a fast slew rate. The shaped output signal may, for example, be inthe dynamic voltage domain.

At 612, the shaped output signal is latched to generate a latched outputsignal. In some embodiments, the latching is done by a flip flop toallow for pulsed or AC coupled inputs. This, in turn, reduces oreliminates static current at the level shifter. The latched outputsignal may, for example, be in the dynamic voltage domain.

At 614, a gate driver circuit is controlled with the latched outputsignal.

While the block diagram 600 of FIG. 600 is illustrated and describedherein as a series of acts or events, it will be appreciated that theillustrated ordering of such acts or events is not to be interpreted ina limiting sense. For example, some acts may occur in different ordersand/or concurrently with other acts or events apart from thoseillustrated and/or described herein. Further, not all illustrated actsmay be required to implement one or more aspects or embodiments of thedescription herein, and one or more of the acts depicted herein may becarried out in one or more separate acts and/or phases.

In some embodiments, the present application provides a level shiftercircuit including: a transistor; a first resistor electrically coupledfrom a first source/drain of the transistor to a power supply node; anda second resistor electrically coupled from a second source/drain of thetransistor to a reference node; wherein the first and second resistorshave substantially the same temperature coefficients and include groupIII-V semiconductor material. In some embodiments, the temperaturecoefficients of the first and second resistors are high, such that thetemperature coefficients change by more than, for example, 1% per degreeCelsius change in temperature. In some embodiments the transistor is aHEMT. In some embodiments, the first and second resistor are 2DEGresistors. In some embodiments, the second resistor has a largerresistance than the first resistor. In some embodiments, the levelshifter circuit further includes a gate driver including an inputelectrically coupled to a common node at which the first resistor andthe first source/drain are electrically coupled.

In some embodiments, the present application provides a gate drivercircuit including: a level shifter including a transistor, a firstresistor, and a second resistor, wherein the first resistor iselectrically coupled from a first source/drain of the transistor to adynamic power supply node, and wherein the second resistor iselectrically coupled from a second source/drain of the transistor to areference node; and a high-side gate driver including power terminalselectrically coupled respectively to the dynamic supply node and adynamic return node, wherein the high-side gate driver is configured tobe controlled by an output of the level shifter. In some embodiments,the transistor, the first resistor, and the second resistor each includea portion of a group III-V heterojunction structure. In someembodiments, the gate driver circuit further includes a bootstrapcircuit including a bootstrap switch and a bootstrap capacitor, whereinthe bootstrap capacitor is electrically coupled from the dynamic supplynode to the dynamic return node, and wherein the bootstrap switch iselectrically coupled to the dynamic supply node. In some embodiments,the bootstrap switch includes a bootstrap diode, wherein a cathode ofthe bootstrap diode is electrically coupled to the dynamic supply node.In some embodiments, the bootstrap switch includes a bootstraptransistor, wherein a source of the bootstrap transistor is electricallycoupled to the dynamic supply node. In some embodiments, the gate drivercircuit further includes a low-side gate driver including powerterminals electrically coupled respectively to a low-side supply nodeand the reference node. In some embodiments, the gate driver circuitfurther includes: a first power transistor including a firstsource/drain electrically coupled to a high voltage node, a secondsource/drain electrically coupled to the dynamic return node, and a gateelectrically coupled to an output of the high-side gate driver; and asecond power transistor including a first source/drain electricallycoupled to the dynamic return node, a second source/drain electricallycoupled to the reference node, and a gate electrically coupled to anoutput of the low-side gate driver. In some embodiments, the gate drivercircuit further includes: a shaper between the output of the levelshifter and the gate driver, wherein an input of the shaper iselectrically coupled to the output of the level shifter; and a latchbetween the shaper and the gate driver, wherein an input of the latch iselectrically coupled to an output of the shaper, and wherein an outputof the latch is electrically coupled to an input of the high-side gatedriver. In some embodiments, the gate driver circuit further includes: asecond level shifter; and a flip flop electrically coupled to an inputof the high-side gate driver, wherein the flip flop is configured to beset by the output of the level shifter, and wherein the flip flop isconfigured to be reset by an output of the second level shifter.

In some embodiments, the present application provides a methodincluding: providing a level shifter including a first resistor, asecond resistor, and a transistor, wherein the first and secondresistors are respectively at source/drain terminals of the transistor;applying a dynamic supply voltage across the level shifter, from aterminal of the first resistor to a terminal of the second resistor,wherein the dynamic supply voltage is generated using a bootstrapcircuit and is in a dynamic voltage domain that alternates between a lowvoltage domain and a high voltage domain; applying an input signal to agate of transistor, wherein the input signal is in the low voltagedomain; and generating an output signal from the input signal, whereinthe output signal is generated at a node common to the first resistorand the transistor, and wherein the output signal is in the dynamicvoltage domain. In some embodiments, the first and second resistors are2DEG resistors and the transistor is a n-type HEMT. In some embodiments,the method further includes: reshaping the output signal into a shapedsignal with a faster slew rate than the output signal; and controlling ahigh-side gate driver using the shaped signal. In some embodiments, themethod further includes latching the shaped signal by a latch, whereinthe high-side gate driver is controlled by a latched signal of thelatch. In some embodiments, the dynamic voltage is generated using abootstrap capacitor and the method further includes: charging thebootstrap capacitor while the dynamic voltage domain is at the lowvoltage domain; and discharging the bootstrap capacitor while thedynamic voltage domain is at the high voltage domain.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A level shifter circuit comprising: a transistor;a first resistor electrically coupled from a first source/drain of thetransistor to a power supply node; and a second resistor electricallycoupled from a second source/drain of the transistor to a referencenode; wherein the first and second resistors have individual resistancesthat change by more than about 1 percent per degrees Celsius change intemperature.
 2. The level shifter circuit according to claim 1, whereinthe individual resistances of the first and second resistors change bysubstantially the same amount per degree change in temperature.
 3. Thelevel shifter circuit according to claim 1, wherein the individualresistances of the first and second resistors change by more than about5 percent per degree change in temperature.
 4. The level shifter circuitaccording to claim 1, wherein the first resistor and the second resistorhave individual temperature coefficients that are high compared to apolysilicon resistor and a metal resistor.
 5. The level shifter circuitaccording to claim 1, wherein the second resistor has a largerresistance than the first resistor.
 6. The level shifter circuitaccording to claim 1, wherein the first resistor and the second resistorcomprise individual portions of a heterojunction structure in which atwo-dimensional carrier gas resides.
 7. The level shifter circuitaccording to claim 1, wherein the second resistor and the transistorcomprise a group III-V material.
 8. A level shifter circuit comprising:a transistor; a first resistor electrically coupled from a firstsource/drain of the transistor to a power supply node; and a secondresistor electrically coupled from a second source/drain of thetransistor to a reference node; wherein the level shifter circuit ispartially formed from a group III-V material.
 9. The level shiftercircuit according to claim 8, wherein the first resistor comprises thegroup III-V material.
 10. The level shifter circuit according to claim9, wherein the transistor comprises the group III-V material.
 11. Thelevel shifter circuit according to claim 8, wherein the second resistorcomprises the group III-V material.
 12. The level shifter circuitaccording to claim 8, wherein the second resistor and the transistorcomprise individual two-dimensional carrier gases.
 13. The level shiftercircuit according to claim 8, wherein the first and second resistorshave individual temperature coefficients that are high, such that theindividual temperature coefficients change by more than about 1% perdegree Celsius change in temperature.
 14. The level shifter circuitaccording to claim 8, wherein a resistance ratio between the firstresistor and the second resistor is configured so a first voltageindividual to and across the first resistor is less than a secondvoltage individual to and across the second resistor when the transistoris in a conducting state.
 15. A gate driver circuit comprising: a levelshifter comprising a transistor, a first resistor, and a secondresistor, wherein the first resistor is electrically coupled from afirst source/drain of the transistor to a dynamic power supply node, andwherein the second resistor is electrically coupled from a secondsource/drain of the transistor to a reference node; and a bootstrapcircuit configured to alternatingly change a voltage at the dynamicpower supply node between a high voltage and a low voltage; wherein aresistance ratio between the first resistor and the second resistor isconfigured so a resistor voltage individual to and across the firstresistor while the dynamic power supply node is at the high voltage issubstantially the same as or less than the low voltage.
 16. The gatedriver circuit according to claim 15, further comprising: a high-sidegate driver comprising a power terminal that is electrically coupled tothe dynamic power supply node, wherein an output of the level shifter atthe first source/drain is configured to control the high-side gatedriver.
 17. The gate driver circuit according to claim 15, wherein thehigh voltage is at least two orders of magnitude greater than the lowvoltage.
 18. The gate driver circuit according to claim 15, wherein thefirst and second transistors have substantially the same temperaturecoefficients, and wherein the first transistor comprises a group III-Vmaterial.
 19. The gate driver circuit according to claim 15, wherein thefirst and second resistors have individual resistances that change bymore than about 2 percent per degree change in temperature.
 20. The gatedriver circuit according to claim 15, wherein the bootstrap circuitcomprises a bootstrap capacitor and a bootstrap switch that areelectrically coupled to the dynamic power supply node, wherein thebootstrap switch is configured to alternatingly change between aconducting state and a non-conducting state, and the bootstrap capacitoris configured to alternatingly charge and discharge, while the dynamicpower supply node changes between the high voltage and the low voltage.